Plastic containers have been conveniently used in not only daily life but also industrial world due to their lightness in weight, economic efficiency, ease of molding, transparency and so on. Among such plastic containers, polyester resin containers, which are versatile as containers for daily use for drinking water, food and the like, especially containers molded from polyethylene terephthalate (PET) whose heat resistance, pressure tightness, flavor-hold properties, etc. have been particularly improved recently, have been the most highly-demanded containers for soft drinks or beverages, and these PET containers are quite regularly used by consumers as potable small containers and containers for hot drinks.
As stated above, synthetic resin containers as represented by polyethylene terephthalate, which play very important roles as containers for drinking water and food, are efficiently manufactured by blow molding usually, which blow fluid into molding dies of preliminarily molded preforms (bottomed cylindrical molding materials; parisons) to carryout expansion molding.
Preforms, as preliminary moldings of plastic containers, have been molded mainly with the use of multi-cavity molds by injection molding and then by blow molding conventionally, but better methods for manufacturing have been longed because price-reduction of molding device, increased production efficiency, transition to low-temperature molding or the like have been demanded.
On the other hand, compression molding machines are traditionally known as molding devices which enable molding at relatively lower cost compared with that in molding by injection molding machines and at relatively lower temperature, while there was a defect that they cannot perform serial production. In response to the defect, a rotary compression molding machine (a rotary- and movable type compression molding machines) has been developed and applied wherein plurality of molding dies are mounted on a rotating disk (see e.g. Japanese Laid-Open Patent Application No. 60-245517), in order to enhance their mass productivity to improve production efficiency.
In molding of such preforms, in order to improve production efficiency further, methods for manufacturing were developed, which use rotary-type material supplies by extrusion molding and rotary type-compression molding machines in performing molding by compression molding (see, Japanese Laid-Open Patent Application Nos. 2000-25729 and 2000-108127). Therefore, production efficiency was improved dramatically by applying rotary-type material supply by extrusion molding and rotary-type compression molding machines. Recently, methods for molding by extrusion-compression molding has been attached the highest importance in preform manufacture.
The molding devices for performing this method for molding preforms are excellent in economic efficiency and production efficiency, which requires continuous material supply (drop insertion) wherein the molten drops extruded from an extrusion die head are rapidly and accurately inserted into female cavities in the compression molding machine which is moving with rotation. Without accuracy, it is impossible to obtain precise preforms since a part of drops overbrim the cavity.
Therefore, performing continuous supply and insertion of the drop more rapidly and accurately has become an important problem in continuous production device of preforms by compression molding machines, however, disclosure of the modified technology aiming at solution of this problem has not seldom been suggested yet, and there are only a few disclosures, e.g. that of modified device wherein a synthetic-resin guiding means having a reverse frustum configuration and having a guiding opening at the drop point of the drop, is provided (see, Japanese Laid-Open Patent Application No. 2000-280248).
As mentioned above, in the molding device for preforms to perform blow molding of synthetic resin containers, it is important to continuously supply molten drops (to insert drops), rapidly and accurately, extruded from an extrusion die head into the female concaves in a compression molding machine which moves with rotation, when adopting manufacturing the devices using rotary-type material supply by extrusion molding and a rotary-type compression molding machine, in order for price-reduction of molding device, increased production efficiency, transition to low-temperature molding or the like. Thus, the problem to be solved in the present invention is to develop technique which enables more accurate and rapid continuous supply.